Coating composition and article coated thereby

ABSTRACT

A coating composition capable of forming a transparent coating having a high refractive index, excellent dyeing properties and scratch resistance on a transparent solid material, the coating composition comprising: 
     (A) 100 parts by weight of an epoxy group-containing silicon compound or a partial hydrolysis product thereof, 
     (B) 0 to 100 parts by weight of an organosilicon compound or a partial hydrolysis product thereof, 
     (C) a metal oxide sol containing 0 to 130 parts by weight of at least one metal oxide selected from the group consisting of antimony oxide, tin oxide and titanium oxide, 
     (D) 0.25 to 30 parts by weight of a polybasic carboxylic acid or an acid anhydride thereof, or a bisphenol compound, and 
     (E) 0.01 to 30 parts by weight of a curing catalyst, or, 
     a molded article formed by coating a transparent solid material with the above coating composition as a coating layer-forming component.

This application is a continuation of application Ser. No. 07/703,816,filed Mar. 21, 1991, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a composition which forms a highlyscratch-resistant and transparent coating having a high refractive indexon a surface of a transparent solid material, and in particular, itrelates to a transparent coating composition for use on a plastic lens.

2. Related Art

A plastic material is utilized as a transparent solid substitute forglass due to its light weight and excellent processability. Since,however, the plastic material is softer than glass, it is easilyscratched. It is therefore known to form a transparent coating layer ona surface of a transparent solid material such as a transparent plasticmaterial, or the like, in order to protect the surface of saidtransparent solid material and impart the surface with wear resistance.For example, Japanese Patent Publication No. 37142/1988 discloses amethod of coating on a transparent solid material with a metal oxidesuch as antimony oxide, or the like and an organosilicon polymer, andJapanese Patent Publication No. 56093/1989 discloses a method of coatinga transparent solid material with antimony oxide or aluminum acetate anda partial condensate of organosilicon.

Japanese Patent Publication Tokkai No. 80359/1983 discloses a coatingcomposition for use on a transparent solid material, which is obtainedby adding alkyl, a vinyl or phenylsilanol partial condensate, a partialcondensate of epoxy-based silanol and a crosslinking agent selected frompolyfunctional carboxylic acid, a polyfunctional carboxylic acidanhydride and polyfunctional imide to colloidal silica.

Further, Japanese Patent Publication Tokkai No. 306477/1989 discloses acoating composition for use on a transparent solid material, whichcomprises antimony oxide, alumina sol, titania sol, etc., and epoxygroup-containing silane, etc.

When the coating composition disclosed in any of the above prior art iscoated on a transparent glass or plastic material having a highrefractive index, interference fringes are observed due to a slightnonuniformity in the thickness of the coating layer when light isreflected, since the refractive index of the coating layer is relativelylow. In particular, when the above transparent solid material is a lensfor spectacles, the lens appearance is impaired and such a lens has nocommercial value.

The coating layers obtained by the above prior art cannot be said to beexcellent in dyeing properties. When a transparent solid material havingsuch a coating layer is applied to sunglasses or window glass,therefore, there have been cases where the coating layer cannot be dyedwith a conventional dye.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a coatingcomposition which can form a transparent coating layer, having a highrefractive index, excellent dyeing properties and high scratchresistance, on a transparent solid material.

DETAILED DESCRIPTION OF THE INVENTION

The above object is achieved by the following scratch-resistant coatingcomposition including the following components:

(A) 100 parts by weight of an epoxy group-containing silicon compound ofthe general formula

    R.sup.1 R.sup.2.sub.n Si(OR.sup.3).sub.3-n

wherein R¹ is an epoxy group-containing group having 2 to 12 carbonatoms, R² is an alkyl, alkenyl or halogenated alkyl group having 1 to 6carbon atoms or a halogenated aryl group, R³ is a hydrogen atom or analkyl, acyl or alkylacyl group having 1 to 4 carbon atoms, and n is aninteger of 0 to 2, or a partial hydrolysis product thereof,

(B) 0 to 100 parts by weight of an organosilicon compound of generalformula

    R.sup.4.sub.p R.sup.2.sub.q Si(OR.sup.3).sub.4-p-q

wherein R² and R³ are as defined in (A), R⁴ is an alkyl or halogenatedalkyl group having 1 to 4 carbon atoms, an aryl or halogenated arylgroup having 6 to 12 carbon atoms, a methacryloxyalkylene group having 5to 8 carbon atoms, a ureidoalkylene, an aromatic ureidoalkylene, or ahalogenated aromatic alkylene or mercaptoalkylene group having 2 to 10carbon atoms, p is an integer of 1 to 3 and q is an integer of 0 to 2,

or a partial hydrolysis product thereof,

(C) a metal oxide sol containing 0 to 130 parts by weight of at leastone metal oxide selected from the group consisting of antimony oxide,tin oxide and titanium oxide,

(D) 0.25 to 30 parts by weight of a polybasic carboxylic acid or ananhydride thereof, or a bisphenol compound, and

(E) 0.01 to 30 parts by weight of a curing catalyst.

The epoxy group-containing silicon compound or the partial hydrolysisproduct thereof as (A) component in the present invention is used toimpart surface hardness. The (A) component can give a cured coatinghaving a high refractive index due to the presence of an epoxy group.

The amount of the (A) component is 100 parts by weight. In addition, theamounts of the following (B) to (H) components are based on 100 parts byweight of the (A) component.

The organosilicon compound as (B) component is used to achieve improvedsurface hardness of the cured coating, as is the (A) component. However,the (B) component is not essential in the present invention. As anorganosilicon compound, the (A) component is sufficient to form a curedcoating even when used alone. The amount of the (B) component is 0 to100 parts by weight.

The metal oxide sol as (C) component is used to form a cured coatinghaving transparency, high surface hardness and a high refractive index.As the (C) component, an antimony oxide (Sb₂ O₅) sol, a tin oxide (SnO₂)sol and titanium oxide (TiO₂) sol may be used alone or in combination.

The dispersion medium for these sols is selected from water, alcoholsolvents and aromatic organic solvents. The amount of the (C) componentmetal oxide(s) as a dispersed phase is 0 to 130 parts by weight.

The polybasic carboxylic acid or the anhydride thereof, or the bisphenolcompound as (D) component is used as a crosslinking agent for the aboveepoxy group-containing silicon compound or the partial hydrolysisproduct thereof as the (A) component and the silicon compound or thepartial hydrolysis product thereof as the (B) component. Moreover, the(D) component is used to impart the cured coating with a high refractiveindex. The (D) component is required to be compatible with each of thecomponents in the coating liquid.

The polybasic carboxylic acid or anhydride thereof is selected, forexample, from dicarboxylic acids, tricarboxylic acids andtetracarboxylic acids. Of these, preferred are a polycyclic aromaticdicarboxylic acid or an anhydride thereof, and a polycyclic halogenatedaromatic dicarboxylic acid or an anhydride thereof, such asnaphthalenedicarboxylic acid, phenanthrenedicarboxylic acid,diphenyldicarboxylic acid, diphenyladipic acid (e.g. 2,4-diphenylhexanediacid) or dibenzoyltartaric acid. Further, the above polycyclicaromatic dicarboxylic acid or the anhydride thereof as the (D) componentmay have substituents other than halogen atoms on their benzene rings.

The above polycyclic aromatic dicarboxylic acid or anhydride thereof arepreferred since a high refractive index can be obtained, as compared toother dicarboxylic acids, tricarboxylic acids and tetracarboxylic acidssuch as itaconic acid, succinic acid, maleic acid, citric acid,tricarballylic acid, etc., and anhydrides thereof. However, theforegoing carboxylic acids or the anhydrides thereof may be used incombination with the above polycyclic aromatic dicarboxylic acid oranhydride thereof.

The bisphenol compound as the (D) component is selected from bisphenolA, bisphenol B, thiobisphenol, etc., of the following formulae. ##STR1##

The amount of the (D) component for use is 25 to 30 parts by weight.

The suitable weight ratio of each of antimony oxide, tin oxide andtitanium oxide as a metal oxide of the (C) component to the total sum ofthe (A), (B) and (D) components is as shown in Table 1.

                  TABLE 1                                                         ______________________________________                                        Metal oxide ((C) component/                                                   total sum of (A), (B) and (D)                                                 components            Weight ratio                                            ______________________________________                                        Sb.sub.2 O.sub.5 /total sum of (A), (B) and (D)                                                     5/95-65/35                                              SnO.sub.2 /total sum of (A), (B) and (D)                                                            5/95-65/35                                              TiO.sub.2 /total sum of (A), (B) and (D)                                                            5/95-35/65                                              ______________________________________                                    

The curing catalyst as (E) component is used for a coating layer formingreaction of the (A) component, the (B) component, the (C) component andthe (D) component. The curing catalyst is selected, for example, fromalkali metal salt or ammonium salt of a carboxylic acid, metal salt ofacetyl acetone, primary, secondary and tertiary amines, polyalkyleneamine, sulfonic acid salt, magnesium perchlorate, ammonium perchlorate,etc. These compounds can be used in combination with an organicmercaptan or mercaptoalkylsilane. This (E) component may be keptseparate from a mixture of the other components of the composition andadded to the mixture just before application of the mixture. The amountof the (E) component is 0.01 to 30 parts by weight.

As an (F) component, 0.5 to 160 parts by weight of an acid catalyst isused for hydrolysis of the silicon compounds as the above (A) and (B)components. The (F) component is selected from formic acid, chloroaceticacid, acetic acid and hydrochloric acid.

As an optional (G) component, 180 to 1,900 parts by weight of a solventis used as a diluent for the coating liquid. The solvent is selectedfrom alcohols, ethers, aromatic hydrocarbons, esters and ketones. When asilicon compound, which is not a partial hydrolysis product, is used asthe above (A) and (B) components, the silicon compound is partiallyhydrolyzed with water as (G) component.

Further, as an (H) component, a leveling and/or surface-smoothing agentfor a cured coating may be used, and either a copolymer ofpolyoxyalkylene and polydimethylsiloxane or a copolymer ofpolyoxyalkylene and fluorocarbon may be used. The amount of the (H)component is 0.01 to 7 parts by weight.

Furthermore, as an (I) component, 0.1 to 2 parts by weight, based on thetotal amount of the (A) to (E) components, of a known antioxidant andweatherability-imparting agent may be used.

In the composition of the present invention, the mixing ratio isselected such that the cured coating has a refractive index of 1.50 to1.63. The transparent solid material in the present invention isselected from acrylic polymers, urethane-based polymers, polycarbonatepolymers and acrylcarbonate polymers, and preferred are those having arelatively high refractive index of 1.53 to 1.65. And, in the presentinvention, the composition and the transparent solid material as asubstrate are used in such a combination that the refractive indexdifference between these two members is not more than 0.04, preferablynot more than 0.03.

The (A) component, i.e. epoxy group-containing silicon compound or thepartial hydrolysis product thereof is used as an essential component,and the (D) component is used as a crosslinking agent for the (C)component, i.e. a sol of the metal oxide, the (A) component, i.e. theepoxy group-containing silicon compound or the partial hydrolysisproduct thereof and the (B) component, i.e. the silicon compound or thepartial hydrolysis product thereof, whereby the cured product of theabove coating composition exhibits a high refractive index.

In the coating composition of the present invention, the epoxygroup-containing compound giving a relatively high refractive index isused as an organic silicon compound or a partial hydrolysis productthereof; the antimony oxide sol, tin oxide sol or titania sol, any ofwhich gives a high refractive index, is used as a metal oxide sol; andfurther, the polycyclic aromatic dicarboxylic acid etc. is used as acrosslinking agent for the formation of a cured coating; whereby it ismade possible to obtain a cured transparent coating having a highrefractive index, being free from interference fringes and having highscratch resistance.

Moreover, the cured transparent coating formed of the coatingcomposition of the present invention further improves the use area andvalue of the transparent solid material in sunglasses, window glass,etc., due to its excellent dyeing properties.

EXAMPLE 1

    ______________________________________                                                               part by weight                                         ______________________________________                                        3-Glycidoxypropyltrimethoxysilane                                                                      11.02                                                Distilled water          2.53                                                 Glacial acetic acid      1.67                                                 (-)-dibenzoyl-L-tartaric acid                                                                          2.53                                                 Sodium acetate (10% aqueous solution                                                                   1.69                                                 Suncolloid AMT-130S (antimony pentoxide sol,                                                           60.13                                                30% Sb.sub.2 O.sub.5 in methanol, supplied by                                 Nissan Chemical Industry, Ltd.)                                               Dow Corning 193 (polydimethylsiloxane-                                                                 0.15                                                 polyoxyalkylene copolymer, 10% in n-butanol,                                  supplied by Dow Corning Co.)                                                  Ethylene glycol monomethyl ether                                                                       20.28                                                Total:                   100.00                                               ______________________________________                                    

At first, glacial acetic acid was added to distilled water, and whilethe resultant mixture was stirred, 3-glycidoxypropyltrimethoxysilane wasadded. Then, Suncolloid AMT-130S and ethylene glycol monomethyl etherwere added, and the resultant mixture was fully stirred. Further,(-)-dibenzoyl-L-tartaric acid was added, and the resultant mixture wasfully stirred until a homogeneous mixture was formed. Sodium acetate wasgradually added to the homogeneous mixture, and the resultant mixturewas fully stirred. Dow Corning 193 was further added, and the resultantmixture was fully stirred, whereby a coating liquid was obtained.

The method for applying the above coating liquid, and the physicalproperty data of the resultant cured coating will be described later,which will be also the case with the following Examples and ComparativeExample.

EXAMPLE 2

    ______________________________________                                                               part by weight                                         ______________________________________                                        3-Glycidoxypropyltrimethoxysilane                                                                      13.2                                                 Suncolloid T-300 (tin oxide sol, 33% nonvolatile                                                       28.1                                                 content in water, supplied by Nissan Chemical                                 Industry, Ltd.)                                                               2,2'-Biphenyldicarboxylic acid                                                                         5.5                                                  Benzyldimethylamine      0.9                                                  Distilled water          13.4                                                 Dow Corning 190 (polydimethylsiloxane-                                                                 0.1                                                  polyoxyalkylene copolymer, 10% in n-butanol,                                  supplied by Dow Corning Co.)                                                  Propylene glycol monomethyl ether                                                                      38.8                                                 Total:                   100.0                                                ______________________________________                                    

3-Glycidoxypropyltrimethoxysilane was added to Suncolloid T-300, and theresultant mixture was fully stirred. Then, distilled water and propyleneglycol monomethyl ether were added to the mixture, and the mixture wasfully stirred. Further, 2,2'-biphenyldicarboxylic acid was added, andthe resultant mixture was fully stirred until a homogeneous mixture wasformed. Benzyldimethylamine was added to the homogeneous mixture, andthe resultant mixture was fully stirred. Dow Corning 190 was furtheradded, and the resultant mixture was fully stirred.

EXAMPLE 3

    ______________________________________                                                               part by weight                                         ______________________________________                                        Tetraisopropyl titanate  13.91                                                Glacial acetic acid      27.89                                                Distilled water          23.20                                                2-(3,4-Epoxycyclohexyl)-ethyltrimethoxysilane                                                          17.52                                                4,4'-biphenyldicarboxylic acid                                                                         4.03                                                 N,N,N',N",N"-Pentamethyldiethylenetriamine                                                             2.70                                                 Dow Corning 190 (polydimethylsiloxane-                                                                 0.10                                                 polyoxyalkylene copolymer, 10% in n-butanol,                                  supplied by Dow Corning Co.)                                                  Ethylene glycol monoethyl ether                                                                        10.65                                                Total:                   100.00                                               ______________________________________                                    

At first, glacial acetic acid and distilled water were added totetraisopropyl titanate, and the resultant mixture was fully stirred.2-(3,4-Epoxycyclohexyl)ethyltrimethoxysilane was added thereto, and theresultant mixture was fully stirred. Further, ethylene glycol monoethylether was added, and the resultant mixture was fully stirred. Further,4,4'-biphenyldicarboxylic acid was added, and the resultant mixture wasfully stirred until a homogeneous mixture was formed.N,N,N',N",N"-pentamethyldiethylenetriamine was added to the homogeneousmixture, and the resultant mixture was fully stirred. Dow Corning 190was further added, and the resultant mixture was fully stirred.

EXAMPLE 4

    ______________________________________                                                               part by weight                                         ______________________________________                                        3-Glycidoxypropyltrimethoxysilane                                                                      16.37                                                Distilled water          3.73                                                 Glacial acetic acid      0.41                                                 Itaconic acid            3.69                                                 Sodium acetate (10% aqueous solution)                                                                  1.11                                                 Suncolloid AMT-130S      45.35                                                Dow Corning 193 (polydimethylsiloxane-                                                                 0.45                                                 polyoxyalkylene copolymer, 10% in n-butanol,                                  supplied by Dow Corning Co.)                                                  Ethylene glycol monomethyl ether                                                                       28.89                                                Total:                   100.00                                               ______________________________________                                    

Glacial acetic acid was added to distilled water, and while theresultant mixture was stirred, 3-glycidoxypropyltrimethoxysilane wasadded. Then, Suncolloid AMT-130S and ethylene glycol monomethyl etherwere added, and the resultant mixture was fully stirred. Further,itaconic acid was added, and the resultant mixture was fully stirreduntil a homogeneous mixture was formed. Sodium acetate was graduallyadded to the homogeneous mixture, and the resultant mixture was fullystirred. Dow Corning 193 was further added, and the resultant mixturewas fully stirred.

EXAMPLE 5

    ______________________________________                                                             part by weight                                           ______________________________________                                        3-Glycidoxypropyltrimethoxysilane                                                                    12.50                                                  Methyltrimethoxysilane 4.40                                                   Distilled water        2.51                                                   Glacial acetic acid    0.36                                                   2,2'-Biphenyldicarboxylic acid                                                                       3.59                                                   Sodium acetate (10% aqueous solution)                                                                2.39                                                   Suncolloid AMT-130S    43.21                                                  Dow Corning 190 (10% in n-butanol)                                                                   0.15                                                   Ethylene glycol monoethyl ether                                                                      30.89                                                  Total:                 100.00                                                 ______________________________________                                    

Glacial acetic acid was added to distilled water, and while theresultant mixture was stirred, 3-glycidoxypropyltrimethoxysilane andmethyltrimethoxysilane were added. Then, Suncolloid AMT-130S andethylene glycol monomethyl ether were added, and the resultant mixturewas fully stirred. 2,2'-Biphenyldicarboxylic acid was further added, andthe resultant mixture was fully stirred until a homogeneous mixture wasformed. Sodium acetate was gradually added to the homogeneous mixture.And, Dow Corning 190 was further added, and the resultant mixture wasfully stirred.

EXAMPLE 6

    ______________________________________                                                               part by weight                                         ______________________________________                                        3-Glycidoxypropyltrimethoxysilane                                                                      16.0                                                 Distilled water          3.7                                                  Glacial acetic acid      0.4                                                  2,2'-bis(4-hydroxyphenyl)propane                                                                       3.7                                                  (bisphenol A)                                                                 Ammonium perchlorate (10% aqueous solution)                                                            0.4                                                  Suncolloid AMT-130S      50.0                                                 Dow Corning 190 (10% in n-butanol)                                                                     0.4                                                  Isopropyl alcohol        25.4                                                 Total:                   100.00                                               ______________________________________                                    

Glacial acetic acid was added to distilled water, and while theresultant mixture was stirred, 3-glycidoxypropyltrimethoxysilane wasadded. Then, Suncolloid AMT-130S and isopropyl alcohol were added, andthe resultant mixture was fully stirred. Further, bisphenol A was added,and the resultant mixture was fully stirred until a homogeneous mixturewas formed. An ammonium perchlorate aqueous solution and Dow Corning 190were added, and the resultant mixture was fully stirred.

EXAMPLE 7

    ______________________________________                                                            part by weight                                            ______________________________________                                        3-Glycidoxypropyltrimethoxysilane                                                                   27.5                                                    Distilled water       6.3                                                     Glacial acetic acid   0.6                                                     4,4'-Biphenyldicarboxylic acid                                                                      6.3                                                     Dibenzylamine         4.2                                                     Dow Corning 190 (10% in n-butanol)                                                                  0.4                                                     Ethylene glycol monoethyl ether                                                                     54.7                                                    Total:                100.00                                                  ______________________________________                                    

Glacial acetic acid was added to distilled water, and while theresultant mixture was stirred, 3-glycidoxypropyltrimethoxysilane wasadded. Then, ethylene glycol monomethyl ether was added, and theresultant mixture was fully stirred. Further, 4,4'-biphenyldicarboxylicacid was added, and the resultant mixture was fully stirred until ahomogeneous mixture was formed. Dibenzylamine was gradually added, andthe resultant mixture was fully stirred. Dow Corning 190 was furtheradded, and the resultant mixture was fully stirred.

EXAMPLE 8

    ______________________________________                                                               part by weight                                         ______________________________________                                        3-Glycidoxypropyltrimethoxysilane                                                                      32.0                                                 Distilled water          7.4                                                  Glacial acetic acid      0.8                                                  2,2'-bis(4-Hydroxypheny)propane                                                                        7.4                                                  (bisphenol A)                                                                 Magnesium perchlorate (10% aqueous solution)                                                           0.6                                                  Dow Corning 190 (10% in n-butanol)                                                                     0.4                                                  Isopropyl alcohol        51.4                                                 Total:                   100.00                                               ______________________________________                                    

Glacial acetic acid was added to distilled water, and while theresultant mixture was stirred, 3-glycidoxypropyltrimethoxysilane wasadded. Then, isopropyl alcohol was added, and the resultant mixture wasfully stirred. Further, bisphenol A was added, and the resultant mixturewas fully stirred until a homogeneous mixture was formed. A magnesiumperchlorate aqueous solution and Dow Corning 190 were added to form ahomogeneous mixture.

COMPARATIVE EXAMPLE

    ______________________________________                                                               part by weight                                         ______________________________________                                        3-Glycidoxypropyltrimethoxysilane                                                                      9.8                                                  Methyltrimethoxysilane   13.0                                                 Glacial acetic acid      1.4                                                  Itaconic acid            2.4                                                  Nalcoag 1041 (silica sol, 35% solid content                                   in water, supplied by Nalco Chemical Co.)                                                              47.4                                                 Acetylacetone aluminum salt                                                                            1.1                                                  Ethylene glycol monoethyl ether                                                                        24.9                                                 Total:                   100.00                                               ______________________________________                                    

Glacial acetic acid was added to a dispersion of silica sol in water,and while the resultant mixture was stirred,3-glycidoxypropyltrimethoxysilane and methyltrimethoxysilane were added.Then, half of ethylene glycol monoethyl ether was added. Thereafter,itaconic acid was added, and the resultant mixture was fully mixed untila homogeneous mixture was formed. Acetylacetone aluminum salt wasdissolved in the remaining half of the ethylene glycol monoethyl ether,and this mixture was added to the above homogeneous mixture. And, theresultant mixture was fully stirred.

Application to lens and performance of coating

(1) Substrate having high refractive index

i) Lens substrate A

A liquid mixture containing 20 parts by weight of2-chlorophenylmaleimide, 20 parts by weight of2,2-bis(3,5-dibromo-4-methacryloyloxyethoxyphenyl)propane, 30 parts byweight of tribromophenyl methacrylate, 25 parts by weight of diallylisophthalate, 5 parts by weight of tertraethylene glycol dimethacrylate,1 part by weight of2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole as anultraviolet light absorber and 2 parts by weight oft-butylperoxy(2-ethylhexanoate) as a radical polymerization initiatorwas molded according to a conventional method (Nd=1.595).

ii) Lens substrate B

Lenses were prepared by molding MR-6 (urethane-based polymer giving ahigh refractive index) supplied by Mitsui Toatsu Chemicals Inc.(Nd=1.594).

(2) Method for application of coating liquids

i) The lens substrates A and B were immersed in an 8% NaOH aqueoussolution for 30 minutes, fully washed with water and dried.

ii) Each of the coating liquids was dip-coated on the substrates at atake-up rate of 25 cm/minute.

iii) The substrates were dried at room temperature for about 20 minutes,and cured under heat at 120° C. for 60 minutes.

(3) Method for measurement of refractive index

Measured with an Abbe refractometer according to a conventional method.

(4) Method for measurement of coating thickness

Measured with a spectrophotometer according to a conventional method.

(5) Crosshatch test

Carried out according to a crosscut adhesion test JIS K5400.

(6) Steel wool test

Coating samples were rubbed with a steel wool #0000 for relativecomparison.

Table 2 shows the results of the performance tests of the abovecoatings.

                  TABLE 2                                                         ______________________________________                                                     Coat-                                                                         ing     Refrac-                                                         Lens  thick-  tive    Inter-                                                  sub-  ness    index   ference                                                                             Cross- Steel                                      strate                                                                              (μm) (Nd)    fringes                                                                             hatch  wool                                ______________________________________                                        Example 1                                                                              A       4.5     1.58  ◯                                                                       100/100                                                                              a                                          B       4.5           ◯                                                                       "                                        Example 2                                                                              A       4.0     1.59  ◯                                                                       "      a                                          B       4.0           ◯                                                                       "                                        Example 3                                                                              A       4.3     1.58  ◯                                                                       "      b                                          B       4.3           ◯                                                                       "                                        Example 4                                                                              A       4.0     1.56  Δ                                                                             "      a                                          B       4.0           Δ                                                                             "                                        Example 5                                                                     Δ  A       4.4     1.57  ◯                                           "       a                                                            Δ  B       4.4           ◯                                           "                                                                    Example 6                                                                     Δ  A       4.2     1.57  ◯                                           "       a                                                            Δ  B       4.2           ◯                                           "                                                                    Example 7                                                                              A       4.4     1.56  Δ                                                                             "      b                                          B       4.4           Δ                                                                             "                                        Example 8                                                                              A       4.3     1.55  Δ                                                                             "      b                                          B       4.3           Δ                                                                             "                                        Comparative                                                                            A       4.5     1.47  X     "      a                                 Example  B       4.5           X     "                                        ______________________________________                                         Evaluation on interference fringes:                                           ◯: not observed                                                   ◯ Δ: observed considerably slightly                         Δ: observed slightly                                                    X: observed clearly                                                           Evaluation with steel wool                                                    a: excellent                                                                  b: inferior to a to some extent                                          

In addition, the coating liquid obtained in Example 4 was coated on alens substrate B and cured by the foregoing method, and the resultantlens was examined to determine its dyeing properties by the followingprocedure. A 1% aqueous solution of BPI Sun Brown was heated to 90° C.,and the above lens was immersed in this solution for 10 minutes, takenout and washed with water. The lens showed 35% transmittance of visiblelight and sufficient dyeing properties.

What is claimed is:
 1. A scratch-resistant coating composition capableof forming a coating having a high refractive index on a transparentsolid material, said coating composition comprising:(A) 100 parts byweight of an epoxy group-containing silicon compound of the generalformula:

    R.sup.1 R.sup.2.sub.n Si(OR.sup.3).sub.3-n

wherein R¹ is an epoxy-containing group having 2 to 12 carbon atoms, R²is an alkyl, alkenyl or halogenated alkyl group having 1 to 6 carbonatoms or a halogenated aryl group, R³ is a hydrogen atom or an alkyl,acyl or alkylacyl group having 1 to 4 carbon atoms, and n is an integerof 0 to 2, or a partial hydrolysis product thereof, (B) 0 to 100 partsby weight of an organosilicon compound of the general formula:

    R.sup.4.sub.p R.sup.2.sub.q Si(OR.sup.3).sub.4-p-q

wherein R² and R³ are as defined above for (A), R⁴ is an alkyl orhalogenated alkyl group having 1 to 4 carbon atoms, an aryl orhalogenated aryl group having 6 to 12 carbon atoms, amethacryloxalkylene group having 5 to 8 carbon atoms, or aureidoalkylene, aromatic ureidoalkylene, halogenated aromatic alkyleneor a mercaptoalkylene group having 2 to 10 carbon atoms, p is an integerof 1 to 3 and q is an integer of 0 to 2, or a partial hydrolysis productthereof, (C) 0 to 130 parts by weight of at least one metal oxideselected from the group consisting of antimony oxide, tin oxide andtitanium oxide, said metal oxide being in the form of a sol, (D) 0.25 to30 parts by weight of a cross-linking agent for (A), said cross-linkingagent being a polycyclic polycarboxylic acid or an anhydride thereof, ora polycyclic halogenated polycarboxylic acid or an anhydride thereof,and (E) 0.01 to 30 parts by weight of a curing catalyst, saidcomposition containing no metal oxide other than (C).
 2. Ascratch-resistant coating composition in accordance with claim 1 whereinsaid cross-linking agent is a polycyclic aromatic polycarboxylic acid oran anhydride thereof or a polycyclic halogenated polycarboxylic aromaticacid or an anhydride thereof.